From nashah, in the sense of failure; rheumatic or crippled (from the incident to Jacob) -- which shrank.
see HEBREW nashah
H5384. nasheh
נָשֶׁה noun [masculine] a vein (or nerve) in the thigh (etymology dubious; on formative compare LagBN 50; Arabic apparently the portion of the principal vein of the leg which is in the thigh, vulgar sciatic vein, or (modern) sciatic nerve and even sciatica, Lane3033); — only הַנָּשֶׁה גִּיד Gen Genesis 32:33a the sinew of the thigh-vein (or thigh-nerve, הַיָּרֵךְ עַלכַּֿף אֲשֶׁר), compare v33b. — On sacredness of thigh, compare RSSem i. 360; 2nd ed. 380 WeHeid (2), 168.
נָשִׁים see אִשָּׁה above